Automatic telephone system.



H. E. HERSHEY.

Auomnlc TELEPHONE SYSTEM.

PPLICATIUN FILED NOV. 28| |913.

1,251,023. V Isfml Deek 25,1917.

z unters-sunt l.

MTNESSQS H. E. 4HEHSHEY. AUTOMATIC TELEPHONE SYSTEM. APPLICATION min nov. 2s. lang.

Patented Dec. 25,1913?.

2 SHEETS-SHEET 2.

UNITED STATES PATENT oEEIoE.

HARRY E. HERSHEY, F WHITE WATER, KANSAS, ASSIGNOR TO AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION 0F ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Specification o! Letters Patent.

Patented Dec. 25, 1917.

Application led November 28, 1913. B crlal No. 803,523.

, To all whom# may concern:

Be it known that I, Haan E. Hamann, a citizen of theUnited Stateaof America, and resident of White Water, Butler county, 6 Kansas', have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a specification.

My invention relates to improvements in i0 automatic telephone systems, and more particularly to means employed for selecting an idle trunk. g fHeretofore, in anaiitomatic telephone sys tem, it liasfvbeli'cuewmary to 1a tary or other 'frmsjof movable line switches `foraautqtnltlgisallyfelecting an` idpletrunk.

By myfinventi n.voidfthe'use offau'ch line. s'iiiiitehea1V iuplishthe trunk'aeleq'cting by'male :gimpeffraie s, with this arrang'ein'en aclfisubci'ibers lineis provided withsuclra' Agrou' -of '1 alayiii and when "the "receiver V1"ei"n'o'vfe from 'the hook -cerf tain-.of 'thesef' der to n i I is'are' 'rated iii or y extnd'corinectoijfrom't eaubscribers line to aniidle-'tlnkrf- In""o`i'd'er to avoid inter- ,ferencebetween' "subscribers having access to-'the-samogroupof trunks, these groups of relays are'controlled by a -master switch in auch a manner'that no-two `aubscribera can so establish connection with the same trunk at one and the same time.

vMy invention will be more clearly underafood by reference to the accompanying draqings, in which I have shown my invention in connection with an automatic telephone system in which my improved relay arrangement is employed for selecting an idle trunk extending from a siibscriliers line to a connector switch, through which connector switch the connection is completed with the called line. lt will, of course, be understood that iii larger exchanges, 'instead of having the selected trunk extciid directly to a connector switch in this manner, suitable selector switches can be interpolated and thus increae the capacity of the cxchange. Likewise, my improved means for selecting an idle trunk could be equally as well employed in other places in the sys-tcm 5o where, heretofore, the usual non-numerical trunk-selecting switches have been emploie-d. Referring to the drawings, Figures l und Z re rcs-ent a roinplcte connection between a calling substation A und a ciillnd solisti `springs 8:,an`d 9 and an impulse'wheel 10,-",l i

tion A in a telephone system embodying the principles of my invention.

The substation A is connected with the central otlice through the conductora 2 and' 3 which terminate in a group of relays C governed by the niiieterv switch D. By means of these relays the line is extended to the connector E, which latter then-com-4 platea the connection to the called subscribers station.

The substation A shown herein may be of any suitable or approved type and com, prises the ii'sual'receiver 4,t`ransmitter5', ringer 6 -andcondensiein7. Being an' automatic substation it is also rovided witliim'fl, impulse"4 transmitter or caliin @device which;A 7o is'represented'herein by afpiiii" of'impulsa 4 vwhich latter` is assumed tobecontrolletf through the "medium of a. finger'hole dial e (not shown); in siich a manner that the img .1'7`5 pulse springe 8 and U may bemomentarilyfi-C" separated a-.niimbcr of times, V'corresponding to each.` digit o f the numberl to be called. it

At the central oice the line's'providet-i' with a brid4 cutfotf relay Y; and'anumbeisu of relays there being one relay foreach trunk that'thc line of the substation A mayff be connected with. The bridge-cutoff relay?!- Y consista of a double-wound coil, they'- bridge-cut-ot windinlg 1l of which operates B5 the amature 12 to t e limitv of its.motion, while the-line winding lI-l'is only'strong` enough to cause the armature i2 to bring the sprin 14 and 15 into engagement without breaking contact between the springs 15 o0 ,and 16. Each relay X consists of aA line winding 17 and a trunk winding 18, it re quiring the combined ctl'orts of the two windings to operate the armature 19.

'lhe master switch l) consists of the Slow 95 acting control rela if'. the motor magnet 2l and the starting reliiy 2;. The motor magnet 21operntes a shaft (not shown), which enlist-s the wipers 23 and 24 to he rotalcd over thi-ii' respective banks of contacts. The nppnriitiiq is so designed that. iipoii the cnergiziitioii of the motor magnet. 21. ilitwipers: 23 find 2l :ire rotated a distance qual to the space between two adjacent l'ziiik ('oiilnits.

The connector switch li is of the .Qniiic gcneriil type of comici-tor vili-li diszvliN-l iii limited .'tiitcs lkllcis lzitviit, No, Hld, granted Murr-li 13, lillll, to lit-ith, llrirkrion and lriclsfou. the circuits, however being in ulied to adapt' the switch to oper te in a sysuY i in which the central oliice amiaratus is con. oiled by impuls .s delirrret'l over two sides of the line in ser: '1, in the manner shown in lh.. .sh Patent No. H19 of 191() to T. G. Martin. rPhe Connector is provided with a shaft `(not shown) carrying -the wipers and 27. The shaft controlled by the vertical niagut-t and the rotary magnet 29. The. usual .side switch comprising the, wipers BO, $1, NQ and 23 is controlled by the private magna-it il in the usual and welldrnon'n manner. The. operations ol the switch are controlled through the medium of the double-woiunl line relay 35, through which the callingr subscriber receives talking current. The called subscriber re-feives talking current through the So- 'callcd back-bridge relay 36.

The, ringing relay 3T is the means through .which ringing current is applied to the called line. Means for permitting the Switches to'be restored to normal position are provided in the release magnet 38, which, upon energizing,

withdraws the retaining pawls from the shaft. The springs 39 and the springs 40 are permitted to close only when the switch shaft has been raised one or more steps from its lowest. position.

Having given a general description of the apparatus, I will now explain in detail the operations by which one substation estab-,

lishes connection withanother in a system embodying the principles ot' my invention. lt will be explained how the substation A may obtain connection with the substation A". It will he assumed that the number of the substation A' is 22.

The drawings indicate a complete connection betwleen a calling and a called line. Under, these conditions the wiper Q3 of the master switch D has been moved from the Contact corresponding to the trunk line employed in establishing this connection onto.

' the next surceedinf* contact which o icration will be more fully hereinafter described. Accordingly, in expiainilugr the manner in which thisy connection between the substation aud the subst ation A is established, it will be assumed that the wiper lll ol the mas-ter switrh l) is at this time restingF upon the contact. Yil and that the wiper il is rest-- iugatpon the rontact'i-l.

Upon the removal oll the receiver from the switrlnhook at the substation preparatory to meltingr a call, a circuit is formed from lground through the Zsprings 43, conductor 2 to and through the substation A, conr, t doctor .5, spmngrs 4l, the line winding` 13 ofthe brit[gre-ontwikl relay Y otl the line A, through the line winding; of the relay X ot the line f\ (which is associated with the tpunlq yll), through the line winding ol the, relay X ol the line A (which is associated with the trunk T2) and -through the springs 45 of the master switch start relay 22 to hattery B. The How ot' current. over this circuit does not energize the relays X sulticiontly to operate their armatures, but this current through the line winding ofthe bridge-cut-ott' relay Y causes the armature 12 to torce the spring 14: into engagement with the spring 15 without separating the spring 15 rom the springn 16. A circuit is thus formed from ground G through the springs 16, 15 and 14and the control relay 20 to battery B. The relay 20, upon energizing, @loses a circuit from ground Gr2 through the springs 46, wiper 23, contact 41 (assuming the wiper 23 to be resting on the contact 41 at the time), through the trunk Winding 18 of the relay X of the grou C associated with the trunk T2, throuvi l the trunk winding 18 of the relay X of t io group C associated with the trunk T, through the trunk winding 18 of the relay X of the, Igrrou C2 associated with the trunk "F2, through t te springs 47 and 48, springs ing 18 energized, andas a result the arma- Y ture 19 is operated. lhen the armature4 19 forces the springs 53 and 54 into engagement, the line of the substation A is extended to the line relay of the connector E.

A circuit'may now be traced from ground G through the lower wlnding 0f the line relay 35, conductor 55 springs 54, conductor 2 t and through the substation A, con.

doctor 3, springs 53c0nductor 56 and the upper winding of the'relay 35 to battery B. The line relay S35, upon becoming energized over the above circuit, closes a circuit from ground G* through the springs 57 land 58 and the relay 59 to battery B. The relay 59, when energized, places ground from (Fi upon the bank contact. 41 to take the place of ground (l2, which will presently be removed. 'l`his circuit: may be traced from ground (l5 through the springs-G0 and the conductor (il to the bank contau'zt 41. The relay 59 also prepares a. circuit for the vertical magnet 2H at. the spring 6T and (i8 and opens the cir-cuit of ihr. release magnet 25S at the springs tl? and 81. 'lhe spring -|9 is adjusted to make contact, with the spring; (l2 before It breaks contact with the spring trunk winding 18 of the relay X of the lgroup C associated with the trunk T2, through the trunk wiiiding'l of the relay X of the group (l associated with the trunk T2, through the trunk wiiidin 18 of the relay X of the group J .ieeociated with the truuk T2, tliroiigh the springs 47 and 48, springs lll and (52 iind the bridge-cuboff winding l1.v ol' the bridgefcutml relay Y of the gri'iup C to batt-,cry B. The insertion of thisI comiliiratively high resistance bridge cui-oil' winding; 1.1 in the circuit decicaees tl'ierurren! through the truuk windings of thc relays X, to il point which will hold the rarmature 19 iii :in operaled'position, but

relays X of the groiii'is (.l or C? would i-,nerggiz/.e when the subscribers to whom these rela ys are allotted rumored their receivers to n'ialie :i fiill, regardless oi' the position of the master switch l). The flor: vot current 'in the circa-it just traced causes the zirrniiture l2 to he operated to the full extent of its motion, thiie removing buttery and ground l'yoiii lthe line :it the springs; 43 und 114-, sind also oiiienin'g; the` circuit ol the control relay 2() nfl. (he springs l5 and iii. The control relay being slow acting maintains the ground fi? upon the bank contact fil for an instant longer, to guard against any delay on the pai-i' el the relay 59 (Figa 2) in putting ground on the twink-release conductor 6l.

The Springe if), 50. (i2 and (355 :ire so ndiiisted that at the time the 'spring 5U breaks cony .ei-tit contarte.

tact with the spring 49, the enring'Z will be in el'igagement `with the' spring 63. At this time ii circuit may be traced from the grounded ii'unlr-releeee condiictzor 6l tliroii;ih the truuk winding,r 18 oi the relay X of the ,f fi'f'nip (1 iiseocinteiil with the trunk T, through the trunk Winding 18 of the Ieliilv ,X of thiJ Irfan ,i C associated 'with the vtrunk T2 through t ie trunk Winding 18 of the relai,v X of the group C2 associated with lliierti'unli' T2, through the springs 47 und' 4S, springs all), (l2 and 63, bank contact 42,

wiper 2l and thestart relay to bzitt'ery B. The :it-art relay 22, upon energizing,

filoni-e` the springefH, thuel closing e circuit through the motor magnet, from ground G through the motor magnet. 2l. springs (3.3 and thcenrinigs 64 to batteri7 B. The motor, niairnet,Y upon energizing, rotates the inni-S .I-l and 24 fromi the 'mink contacts ll and l2. rr-eiieiztively; to the next adju Assuming that this Contact han a Limi-dini; ground upon it, the start iria); 23 will rriniiin enorgizf il. eilen thut the motor-muguet. pon energizing; ilo opone its own circuit at, the springe 3.7. :i res-ult the motor magnet will act in :i iniinner similarto that of a buzzer to to raise the shaft wipers two steps.

*i wiii be' rotate the wi ers 28 and 24 until an 1mgrounded ban contact' is reached, at which' point the start' relay denergizes and opens the circuit ofV the motor magnet 'at 'the springs 64. The start relay, upon energizing, oiens the springs 45, in this way removing while thcmaetci' switch is rotating.

The calling subscriber now o rates-hiei calling device furthe first' d i it 2 of vthe called number, whereby the su station impulse springs 8 i1.nd,9 are operated twice momentarily, each time breaking the circuit of the connector line relay 35. Euch vtime the line relay of the connector denergizes in response to the breaking, of its circuit b attery from ull the line 'relays soV the im ulse sprin 's 8 and 9, n circuit. is

clore-i1 rom groun G* through'the springs .57 :ind 6G, springs and 68 (the slow ecting relay 59 remaining energized between iin-pulses), relay 69, vertical magnet`28 and. the side switch Wiper 30 in first position) to battery. B. The vertice ei'gized twice over this circuit and 'operates slow acting relay 69 is energized in series with the vertical' magnet Qlandl does not. denergizc until after the last iinpulseis delivered. Up'on' "energizing, the `relay .69 closes i1 circuit from ground Gf through the springs 70vand 71'and the privatema iet 34 to bntteryB. YWhen this circuit is after the last vertical impulse 'has been cle'- livei'ed to the vertical ma et, the'private magnet 34 dcnergizes an the side Switch passes to second position. Bytliis actionthe side switch wiper 30 transfers the buttery connection from the vertical magnetQS to the rotaryinagnct 29. When the calling device is operated for the last digit, the relay 35 of the'connector E operates jin the saine manner as for. lthe previous digit.

Euch time the connectorline relay 35 deenergizes in response to the impulses,l :i circuit is closed from ground Gy* through Athe springs 57 and 66, springs 67 and' 68,' relay 69, Springe 72', rotary magnet 294 and the side switch wiper 30 (in second. position) magnet 2B is enroken to battery B. The rotary magnet 29 is eneri gized tivo times .over this.` circuit und oper-` i :il to rotatethe wipers ontothmcout'actsof the desired line.

rl he relayffloperaws in the saine manner as for the previous digit to close the circuit ci 'the private' magnet 34 AWhile the rotary muguet 1s operating, If

the culled line is idle, the private magnet 1M deinergizes when its circiutis broken by the relay 69 after the last impulse is delivered to the rotary .Iniigneh and the sideswitcli paseos to third position', completing tlle counection with the called line through the sidi; lSwitch wipers 31 and 32, shaft Wipers '25 movement of the eide switch `wiper 33 to third position provides a. guarding potential imd 27 and the izoi'iductors 73 and 74. TheV i for the connector pri vate bank contacts of the called Aline, and closes an energizing circuit for the bridge-cobol?winding of the bridgecut-ott' relay ot' the line switch Cw. rlhis circuit extends from ground G throuoh the si-deswiteh wiper 33 (in third posit-ion), private wiper 26, private bank ^Contact 75 and thence to all multiples ot' the same. This circuit also extends through the bridgeeut-ott' winding 76 of the linel A to battery B. The winding 7G, upon energizing, opera-tes to disconnect the relay group Um from the line. At the instant that the side switch wiper 3() of the connector E reaches third position, a circuit is. closed from ground G", interrupter TT, through the ringer relay 37, springs TS and the side.l switch wiper 3() (in third position) to battery B. Since this circuit includes the interrupter 77, the relay 37 is energized intel'- mittently, each time operating to disconnect the calling line from the 'alledline and'to bridge the ringing generator R across the called line. Vi hen the called subscriber re.- movesl his receiver, the called substation is provided with talking current through the. windings of the back-bridge relay 256, which relay, ii'pon energizing, closes the circuit of the ringing cut-otl' relay 79, said circuit extending from ground GB through the side switch wiper (in third position).I springs S0 and the relay 7 9 to battery B. ,The relay 79', ltipon energizing, interrupts the circuit. of the ringing relay 3T, at. the. springs 7h and vtelosts `a -locking circuit toritself through its own springs, independent ot the springs St) o't' 'the back-bridge relay lli.

' After the. conversation is completed, the commctiop'is releasedby the hanging up of the receive' at the calling substation in the. following manner: When the receiver at the substation A is restored to the switchhook, lhe'energizing circuit, otl the connector line relay is opened, which relay. upon deenergizing, breaks the circuit. ot' the relay 59, vwhich iii turn'deenergizes ami closes the circuit of the release magnet 3S. 'lhis cir-- cuit. extends t'rom ground (if through the springs 57 and (itl, springs (i7 and 8l, ott'- nornlal springsI 39 and the release magnet 38 to battery ll. The release magnet 38, Upon energizing, operates to release the connector, whereupon its own circuit is broken at the ott-normal springs 39 when the switch shaft reael'ies .itslowest,,-position. 'lhe re;- iuovz `l )t ground (if', due to the deenergting ofth elay 5l), opens the clreult through the brindge-cut-ofi' relay Y of the line A insel-ies with alllle trunk windings oi the relays X associattah with the trunk T, \\'herel.|pon the` cut-oil' relay i.' rcturnsftoiormal position.

It having been explained how oneksub scriber. stablishes connection and releases the same1 it, will now be explained how a 4 connection is preventul from' beu-1g made a group ot" trunk lil with a busy line and how the calling subscriber receives the busy signal when ea1ling a busy number. If the number called is busy, there will be a guarding potential upon the connector private bank contact. The connectorv private wiper, uponengaging this 'guarding contact and before. the side switch wipers have passed to third position. completes an energizing circuit through the busy relay 82. This circuit extends froln ground at the private wiper 26, through the side switch wiper 33 (in second position), through the rings '83 and 84, relay S2. springs 85 and 11 and the private n'iagnet i-l to battery B. The private magnet Bt remains energized, thus holding the side switch inse-cond position, and keeping the .line to the called subscriber open. The relay-82 energizes and opens the circuit of the rotary magnet .29 at the-springs 72, and also t'orms a locking circuit for itself from ground (im through the off-normal springs 40, springs Sti and St. relay 82, springs 85 and 7l and the private magnet 34A to'battry li. '.lhe engagement ofthe springs 87 serves to close a circuit for the busy tone from the busy machine Q through said 'springs 'and'the side switch wiper 32 (in second position), through the calling tele-- phone and back tothe busy machine vQ. The calling subscriber, upon receiving the busy signal, hangs the receiver upon the hook, thereby releasing'the connection in the manner above described.

TW ith the arrangement described, it will be seen that the master switch D, through the wiper '2.3, supplies a circuit which indiea'tes the next idle. 'trunk to,- be used in extending a connection to a selector..` This master switch also, throughthe medium of 'the wiper 24, is driven from a busy trunk.

Alectin g idle trunks between selectorv switches,

in the manner in which other forms of non` numericalswitches are'eoinmonly employed, and various other modifications and changes can be made without.V departing from the spirit of 'my invention. 'y What I claim silly/invention is l. In aftelephone sygem, n group oflines,

' a group of doiible wound relays for each line, one winding of the relays of each group being connected in ing may@ euries, und Llic otlicr winding of cach rela in a group lit-ing (-.onncctcil in 4crit-.s witi tho winding of thc corresponding rclay 11i the, otlicr group, and incans controlli' by said rclays for cstcnding thc conncction from said lincs to :in ldlc onc of said trunks.

2. ln a tclephonc. gystcui, a group of lincs, a groupol' trunk lincs, a group of doublowoiind rclays for ciicli liuc, onc winding of tho l'clays of cach group living conncctcd in serios, und thc othier winding ol cach rclay in a group licing conncctcil in scrics with thc winding of thc coricsponding rclay in thc olhcr group, nii-.ans controllcd hy said relays foi' cxtcnding thc' i-,oiiiu-.ction troni said lincs to an idle ono of said trunks, and a master switch for controlling thc operation of said relays.

Il. ln a. telephone syslcin, a group of lincs a group of trunk lines, a group o double-wound' rcla s for. cach linc, vonfc winding iQf-"-jllic rclyiiys 'of cach 'group licing .connected 'in- .sci-ics, vand tlic otlicrl windingin a group being 4.' Iii tlcpline a group of lines,

linges, "a fgroup Yol'V doublefoi" cath Vl ilii.s,. onc )vindin f of thc. rclay fcircli group being coniicctc in sci'ics, nur thy otlir-winding of cach relu.- in n. cup ming conncctcd in series w'iti the winding-'of thc corri-,spondi'ig rclay in tlic' ottici; group, nii-inns controlli-.d by said rclays for cxtcnding'tlic conlicction from said lincs to au idlc onc of said trunks, a inastcr switch for ci'introlling thc opi-.ration ol' said relays, und a cut-oill rclay for cutting oll' said rclays troni thc liuc.

5. ln a tclcplionc system, a liuc., a plurality of trunks ussociatcd with said liuc, inciius for locating an idlc trunk, :i magia-tic coil for said liuc corrcspnnding t.o said idlc trunk, a unignctic coil individual to said trunk corresponding to said liuc, a circuit closcr jointly controllcd h y said coils, :ni cncrgiziiig circuit [or said linc coil comprising thc. linc circuit. and :i lincl lclay in said circuit l'oicontrolling said nicans.

(3. ln a tclcplionisystcni, a liuc. a plurality of trunks associatcd willi said linc, lncans for locating :in iill'.' truuk, a niaizuct-ic coil for Suid linc coricsponiling to saiil idlc trunk1 a nnignctic coil individual to said trunk corrcsponding to said linc, n circuit closcr jointly conlz'ollcd luy .said coils, an cncrgiL/,ing i-,ircuil for said linicoil coni prising tlic. liincircuit, a linil rcliiy in said circuit, for controlling said nii-ans. and an energizing circuit. for said trunk coil undcr thc control of said iueans.

l, hy

hc' othcr group,

Vcorrcspondiiii!l to said trunk, cach' con 7. In n telephone system, a line, a plurality of trunks associated with said line, means for locating an idlc trunk, a magnetic coil for said linc correspondin to said idle trunk, a magnetic coil individual to B aid trunk correspondingI to said line, n circuit closer jointl controlled by said coils; an cncrgizi'n circuit for said line coil cornprising tic linecircuit, and a line relay in said circuit for controlling said mcans,the Iiiv joint action of said coils always operating to conncct said particular line with said particular trunk.

8. In tclcplione syst/cm, a line, a plurality of ltrunks associato-d with said line, means 8O for locating an idle trunk, a magnetic coil for said linc corresponding to-Said idle trunk, a uiagiictic coil individual to said trunk corresponding to said line, a circuit closcr jointly controllcdliy said coils, un energizing circuit for said linc coil comprising t'lic linc circuit., a linc rclay in sind cirl cuit for controlling said uicans, nl ld'iufijlcllcrgizing circiil. for said unk c o'ilfun' thc control of said nica L* "i trolled jointly by tlic coil of thc cor.; nsponding liuc and' by thc truuk coil corriislpondin r to said lino, energizing circuits or sai( liuc. coils, cach circuit including thc coricspondiug linc, and a liuc relay in thc liiic circuit. for controlling said nicans.

tt). ln a tclcpliolic systcni1 a plurality of lincs, a plurality of trunks for said linizs, incans colnlnon to said lincs for locating im idlc trunk, an cli-ctroinagnctic coil for cach linc i-.orrcsponding to said iillc. trunk, clcc- Lroniagiut-ic coils for cach trunk olc for cach liuc., a circuit. closi'r l'or cach linc cor- 'ri-.sponding to said trunk` cach controllcd jointly liy thc coil ol tlic corrcspondilig line and hy tln` trunk coil corrcs|mnding to said liuc., cncr; 'i'/.in;r circuits for said lmucoils, cacli circuit including thc. corrcspondinpr liuc, :i liuc :clay in thc linc circuit, l'or controlling said incans, and :in cncrgizing circuit for said trunk coils undci' thc control of said incans.

ll. ln :i tclcplionc system, a plurality of lncs, a plurality of trunks for said lincs, ini-ans cnininon lo said lincs for locating an idlcI trunk, :in elcctroniainictic coil for cach iinc. cori csponding to said idlc truuk, electroiiiailni-.tic coils for cach trank one for cach liuc, a circuit. closer for cach line corresponding to said trank, each controlled jointly by iis the coil of the corresponding line and by the trunk coil corresponding to said line', energizing circuits for said line coils, each circuit including the corresponding line, and a line relay inthe ling circuit for controlling said means; said mea-1' f., svyitchcorninon to1 said lines.

` telephone vste'm,` a. plurality of plurality o fiks for said lines, mean common to'said 'fs' for locating an fi. elect`roi agn`\f coil for each'.

pending to saldidle trunk, elec- 'c '"cils'orfeachtrunk one for a'circiiit closer for .each line cor ding to said trunk, each controlled no cil comprisl ne relay 1n said cir.- d"

, offftrlin means. orlocatin'gf an idle trunk, a magnetic coil fr'said linecorrespondingto said idle trunk, a-.magnetic coil individual to said trunk'corresponding 'to said line, a circuit closeri'jo'intly cont-rolled -by said coils, an

energizin'g'circuit for-said lmecoil compris-` ing the lme circuit, a line relay in said circuit for controlling said means, an energizing circuit for said trunk coil under the control of said means, and means for making the trunk busy.

15.' In a telephone system, a line, a plu rality of trunks associated with said line, means for locatingl an idle trunk, a magnetic coil for said line corresponding to said idle trunk, a. magnetic coil individual to said trunk corresponding to said line, a circuit closer jointly controlled by said coils, an energizing circuit for said line coil comprising the line circuit, a line `relay in said circuit for controllin said means, the joint aetion of said coils a Ways operating to connect said particular line with said particular trunk, and means for making the trunk busy.

16. In a telephone system, a line, a plurality of trunks associated with said line, means for locating an idle trunk, a magnetic coil for said line corresponding to said idle comprising a master` Vthe coil ofthe corresponding line b I Silid coils, 1 an' .and menne ,.trunkfor coimectingfsaid-'line' whe cal cuit for controlling said means,van energiza ing circuit for said trunk coil under the corr. trol ofsaid means,tl1e joint'action Aof' said I coils always operating to-connect said par-v v,ticular line with said particular trunk, and means for making the trunk busy. 17. In av telephone system, the combination with a pluralitytof lilies and apluralitiy of ltrunk lines, of means for connectin a cal VAing line with an idle. trunk line, s ai means comprising a. relay hayingjone Winding in l d iyidual. to the calling- .line and. @second inding individualto the idle -t1'1 1nk .,line,

aiplurality ofrela i. line; each relay? bei tocoiinect, tljie 'calling eraztin'gfthe l A'en i'rth a :with 'any one of said trunk `lines,a1 i neans-A for controlling the selection of-"triinklines wherein' the said line upon the initiation' of "dimeans for energizing saidwindings."

successive calls will be connected with said trunk lines in rotation. l f

20'. In a. telephone system, a plurality of subscribers lines,-a plurality of trunk'lines, means'compri'sing a plurality of relays one for 'each trunk for connecting ,any calling subscriber with any trunk line, and means for selecting idle trunk lines for connection in regular orderv without regard to the numberof simultaneous calls.

21. In a telephone system, a subscribers line, a plurality of trunk lines, means coinprising a plurality of relays for connecting said line when calling with any one of said trunk lines, and means for controlling the selection of trunk lines, whereby the said line upon the initiation of successive calls will be connected with said trunk lines in rotation, each ltime by a different one of said relays.

22. In a telephone system, a plurality of subscribers lines, a plurality of trunk lines, means comprising a plurality of relays for connecting any calling subscriber with any trunk line1 and means for selecting idle trunk lines for ,annection in regular order without regard to the number of simultaneous calls, each time by a different one of said relays.

23. In a telephone system, a plurality of' subscribers lines, a plurality of trunk lines associated with said lines, means for locating an idle trunk line, as many magnetic coils individual to each subscribers line as there are trunk lines accessible to each subscribers line, as many magnetic coils individual to cach trunk line as there are subscribers lines having access to said trunk line, and a circuit closer jointly controlled by a pair of said coils.-

24. In a telephone system,I a plurality of subscribers lines, a plurality of trunk lines associated with said lines, means for locating an idle trunk line, as many magnetic coils individual to each subscribers line as there are trunk lines accessible to each subscribers line, as Vmany magnetic coils individual to ,each trunk line as there are subscribers lines having access to said trunk line, and a circuit closer jointly controlled by a pair of said coi'is for connecting a calling subscribers line with an idle trunk line "25. In a telephone system, a. plurality of subscribers lines, a plurality f trunk lines associated with said lines, means for locating an idle trunk line, as many magnetic coils individual to each Subscribers line as there are trunk lines accessible to cach subscribers line, as many magnetic coils individualto cach trunk line as there are subscribers 'lines having access to said trunk line, and a circuit closer jointly controlled by a pair of said coils, the joint action of said pair of coils always operating t0 connect a particular' subscribers line with a pariicuiar trunk line.

QG. In a telephone system, a plurality of subscribers lines, a plurality of trunk lines associated with said lines, means for locating an idle trunk line, as many magnetic coils individual to each subscribers line as there are trunk lines accessible to each subscribers line, as many magnetic coils individual to cach trunk line as there are subscribers lines having access to said trunk line, a circuit closer jointly controlled by a pair of said coils, and an energizing circuit for the coils individual to a particular trunk line under. control of said means.

27. In a telephone system, a plurality of subscribers lines, a plurality o trunk lines associated with said lines, means for locating an idle trunk line. as many magnetic coils individual to each suhscribers line as there are trunk lines accessible to each subscribers line, as lnany magnetic coils individual to each trunk line as there are subscribers lines having access to said trunk line, a circuitcloser jointly controlled by a pair of said coils, and an energizing circuit for the coils individmzz to a particular line, said circuit including the said line. y

Signed by me at Chicago, Cook county, Illinois, this 17th day of November, 1913.

HARRY E. HERSHEY. 

